1. Field of the Invention
The present invention relates to an optical deflector capable of being fabricated by techniques of micromechanics, an image forming apparatus using the optical deflector, and the like.
2. Description of the Related Background Art
In recent years, as represented by high integration of semiconductor devices, enhancement of performance and miniaturization of a variety of devices or apparatuses have been advanced as development of microelectronics proceeds. The same also holds true in apparatuses using micro-machine devices (for example, a micro optical deflector, a micro mechanical-amount sensor, and a microactuator having a swinging member swingingly rotatable about a twisting torsional axis) fabricated by techniques of micromechanics using silicon process.
Enhancement of performance and miniaturization also advance in fields of (a) a laser beam printer, (b) an image displaying apparatus, such as a head mount display, and (c) a light input device, such as a barcode reader, each of which uses an optical deflector for achieving optical scan, for example. Furthermore, it is desired to apply those techniques to fabrication of products which are further miniaturized and formed in a readily-portable form, for example.
Japanese Patent Application Laid-Open No. 2000-249964 (its U.S. counterpart is U.S. Pat. No. 6,456,413) discloses an optical deflector having a swinging member capable of being swingingly rotated about a twisting torsional axis, as illustrated in FIGS. 1A to 1C. FIG. 1A is a top plan view of the optical deflector, FIG. 1B is a bottom plan view of the optical deflector, and FIG. 1C is a perspective view illustrating a mounting process of mounting the optical deflector to a mounting structure. In the optical deflector, a movable member 1001 and elastic support members 1002 and 1003 for rotatably supporting the movable member 1001 are integrally formed in a silicon substrate 1000. A reflective face 1004 is formed on a front face of the movable member 1001, and a driving coil 1005 is provided on a rear face of the movable member 1001. A magnetic-field generating unit for applying a magnetic field to the driving coil 1005 is further provided, and the movable member 1001 can be driven by a magnetic force generated when a current is caused to flow in the driving coil 1005.
In the mounting structure of the above-discussed optical deflector, a space portion 1011 for allowing the swinging rotation of the movable member 1001 is formed in a deflector-arranging region of a mounting substrate 1010 for fixing the optical deflector thereto, and a conductive pattern 1012 is formed near the deflector-arranging region. When the optical deflector is fixed to the mounting substrate 1010, an electrode terminal 1006 of the driving coil 1005 formed on a rear face of the semiconductor substrate 1000 of the optical deflector is brought into contact with the conductive pattern 1012.
In (a) a laser beam printer, (b) an image displaying apparatus, such as a head mount display, and (c) a light input device, such as a barcode reader, which perform optical scanning by using the above-discussed micro-machine device, a flatness is required for the reflective face for deflecting light.
However, in the event that a support substrate for forming a movable member and an elastic support member is fixed, a stress occurring at the time of fixation, a thermal stress and the like are likely to act on the substrate, leading to deformation of the movable member. Accordingly, a face precision or flatness of the reflective face serving as a light deflecting unit decreases.